Anionic polymerization is a common technology used in producing plastic materials, and elastomers, and the polymers made by anionic polymerization also have various commercial applications, such as tire and other industrial elastomers, adhesives, sealants and coatings.
With regard to the anionic polymerization, an initiator is required for initiating the polymerization of monomer. It is known that most common initiators have some metal components, such as an alkali metal ion, an alkaline-earth metal ion and the compounds thereof. However, the physical properties and thermal stability of the polymers that are produced by using an initiator containing metal ions will be affected by the remaining metal ions. Therefore, some specific methods and complicated procedures are required in order to remove the metal ions during the polymerization.
In order to obtain a polymer with an uniform molecular weight distribution, a terminating agent is added into the anionic polymerization for terminating the reaction. A traditional terminating agent having an alcohol group, a halogen group or an ester group may completely terminate the anionic polymerization, however it forms a complex with the alkali metal ion that cannot be separated from the anionic polymer solution. Further, the transparency of the polymer made by anionic polymerization will be reduced even if the polymer solution goes through the separation process. Besides, the final product or the by-product of the complex formed of the anionic polymerization and the terminating agent having alcohol groups, halogen group or ester groups often exists in the solvent and become a poison. After the recovery procedure of the solvent, the poison remaining in the waste water will cause a higher chemical oxygen demand (COD) or biochemical oxygen demand (BOD). Since the traditional terminating agents are liquids and will mix with the solvent used in the polymerization, it is not economical to consume extra energies for removing the terminating agent.
In view of the above, the inventors developed a terminating agent for anionic polymerization based on their experience in studying the polymerization for over a period of time. The terminating agent of the present invention not only has an effect of terminating the anionic polymerization, but also has a low solubility in common solvent used in the polymerization. Thus, the complex formed of the terminating agent and the alkali metal ion can be separated easily from the polymer without complicated separation steps. The separation of the present invention will not affect the transparency of the polymer, moreover, the terminating agent of the present invention is a natural and harmless material that will not contaminate the environment so that make the product more environmentally friendly than the traditional terminating agents. The summary of the present invention is described below.